No, it would be great for the plants to have blue light in veg.
However, I would turn the mover OFF during the veg period and cluster the plants in their smaller pots under the MH until they are as big as you want, then flip to flower for the first couple weeks with them still under the MH, and then re-pot them into the right size pots to finish, spread them out, and turn on that light mover with the HPS in it.
This will save you $$$ in electricity by using it the most efficiently, and reduce your veg time by clustering more plants under more intense light.
Read the continuous canopy sticky in basic for pics!

If you have space to build a second room though, don't bother getting a switchable K MH- just build a room that is about half the size of your flower room and keep that MH 400 in there permanently. A good ratio of HID veg watts : HID flower watts is about 1:3 so if you veg under 400w you should flower under ~1200w, but 1000 is just fine, especially on a mover! You know... in that space, with that mover, you could run a PAIR of 1000s... there are hoods that accept 2 bulbs, or you could run 2k side my side. But then you get hot spots back again.
Just rambling... lol...